I’ve seen the power washing method before but you have to be very careful around the antlers. If you get to close and hit the base of the antler with a direct jet of water it will take the natural coloring that is there leaving a distinctly lighter line where you sprayed. This is especially true with some of the dark timer bull elk antlers where they are almost black because of the trees they rub on.
I think the best cleaning you can do is also the most time intensive and expensive to maintain is the flesh eating beetles. It is the best way to ensure there is no damage to your trophy too. I wouldn’t recommend that method unless you are a full time taxidermist because you have to keep feeding them all year.